Efficient, controlled conveyance of optical energy through apertures in otherwise opaque materials is an important aspect of many optical measurement instruments. This observation is especially applicable to near-field microscopy, which employs apertures smaller than a free space optical wavelength of an optical beam used in the near-field microscopy, hereinafter referred to as sub-wavelength apertures, to achieve imaging with high spatial resolution. The low optical efficiency, typically of the order 10−4 or lower, of sub-wavelength probes used as near-field scanning probes can have a negative impact on signal-to-noise ratios and measurement bandwidth.